springboot-jpa的实现操作

JPA全称为Java Persistence API（Java持久层API），它是Sun公司在JavaEE 5中提出的Java持久化规范。

它为Java开发人员提供了一种对象/关联映射工具，来管理Java应用中的关系数据，JPA吸取了目前Java持久化技术的优点，旨在规范、简化Java对象的持久化工作。

JPA对于单表的或者简单的SQL查询非常友好，甚至可以说非常智能。他为你准备好了大量的拿来即用的持久层操作方法。甚至只要写findByName这样一个接口方法，他就能智能的帮你执行根据名称查找实体类对应的表数据，完全不用写SQL。

它相对于mybatis来说不用写xml等配置，简直方便的不行，对于我们开发者来说，谁更简单，开发效率更高，我们就喜欢谁(不喜欢不行，看看产品经理手里的菜刀)！！！

这时候mybatis就不服了，我确实需要写一大堆乱七八糟的xml，但是也可以用注解啊。

还不是要写sql，总是一写增删改查sql，有没有把这些常见的增删改查全部封装起来，我们直接调用api，sql让它们自动组装就好了，说实话我自己封装了一个基于mybatis的组件，常见的增删改查，自己组装成sql去查询，后来由于没有oracle，sqlserver的数据库环境，对这些数据库的时间等等函数支持不好，又有jpa和mybatisplus这些现有的，我也就偷懒了

好了我们之前有实现过springboot-mybatis

springboot-mybatisplus的整合，现在就来实现一下jpa的，你们看看哪个比较方便好用，可以自己用用看

这是我实现的demo预览

由于我想看到效果，又不想装postman来测试，我就集成了swagger

最终效果如上图

好了，我直接放代码了

<?xml version='1.0' encoding='UTF-8'?><project xmlns='http://maven.apache.org/POM/4.0.0' xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' xsi:schemaLocation='http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd'> <modelVersion>4.0.0</modelVersion> <groupId>com.zkb</groupId> <artifactId>spring-data-jpa</artifactId> <version>1.0-SNAPSHOT</version> <build> <plugins> <plugin><groupId>org.apache.maven.plugins</groupId><artifactId>maven-compiler-plugin</artifactId><configuration> <source>8</source> <target>8</target></configuration> </plugin> </plugins> </build> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> <version>2.1.1.RELEASE</version> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-jpa</artifactId> <version>2.1.1.RELEASE</version> </dependency> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>8.0.18</version> </dependency> <dependency> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId> <version>1.18.12</version> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-devtools</artifactId> <version>2.0.4.RELEASE</version> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <version>2.1.2.RELEASE</version> <scope>test</scope> </dependency> <dependency> <groupId>com.alibaba</groupId> <artifactId>druid</artifactId> <version>1.0.31</version> </dependency> <dependency> <groupId>org.junit.jupiter</groupId> <artifactId>junit-jupiter</artifactId> <version>RELEASE</version> <scope>compile</scope> </dependency> <dependency> <groupId>org.junit.jupiter</groupId> <artifactId>junit-jupiter</artifactId> <version>RELEASE</version> <scope>compile</scope> </dependency> <dependency> <groupId>org.slf4j</groupId> <artifactId>slf4j-api</artifactId> <version>1.7.25</version> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-test</artifactId> <version>2.2.2.RELEASE</version> <scope>compile</scope> </dependency> <dependency> <groupId>io.springfox</groupId> <artifactId>springfox-swagger2</artifactId> <version>2.9.2</version> <exclusions><exclusion> <groupId>io.swagger</groupId> <artifactId>swagger-annotations</artifactId></exclusion><exclusion> <groupId>io.swagger</groupId> <artifactId>swagger-models</artifactId></exclusion> </exclusions> </dependency> <dependency> <groupId>io.swagger</groupId> <artifactId>swagger-annotations</artifactId> <version>1.5.22</version> </dependency> <dependency> <groupId>io.swagger</groupId> <artifactId>swagger-models</artifactId> <version>1.5.22</version> </dependency> <!-- swagger-ui --> <dependency> <groupId>io.springfox</groupId> <artifactId>springfox-swagger-ui</artifactId> <version>2.9.2</version> </dependency> <dependency> <groupId>com.github.xiaoymin</groupId> <artifactId>swagger-bootstrap-ui</artifactId> <version>1.9.1</version> </dependency> </dependencies> </project>

server: port: 5001spring: datasource: type: com.alibaba.druid.pool.DruidDataSource #Druid 是阿里巴巴开源平台上一个数据库连接池实现，结合了 C3P0、DBCP、PROXOOL 等 DB 池的优点，同时加入了日志监控 driver-class-name: com.mysql.cj.jdbc.Driver url: jdbc:mysql://localhost:3306/test-demo?useUnicode=true&characterEncoding=utf-8&useSSL=false&serverTimezone=UTC&autoReconnect=true&failOverReadOnly=false&zeroDateTimeBehavior=convertToNull username: root password: root dbcp2: min-idle: 5 initial-size: 5 max-total: 5 max-wait-millis: 200 jpa: database: mysql database-platform: org.hibernate.dialect.MySQL5InnoDBDialect show-sql: true hibernate: ddl-auto: update

package com.zkb.entity; import com.fasterxml.jackson.databind.annotation.JsonSerialize;import com.fasterxml.jackson.databind.ser.std.ToStringSerializer;import io.swagger.annotations.ApiModel;import io.swagger.annotations.ApiModelProperty;import lombok.Data; import javax.persistence.*; /** * 实体类 */@Entity@Table(name = 't_user')@Data@ApiModel(value = '用户信息', description = '用户信息')public class User { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) @ApiModelProperty(value = '主键') @JsonSerialize(using = ToStringSerializer.class) private Long id; @Column(name = 'username') @ApiModelProperty(value = '用户名') private String username; @Column(name = 'password') @ApiModelProperty(value = '密码') private String password; }

package com.zkb.dao; import com.zkb.entity.User;import org.springframework.data.jpa.repository.JpaRepository; public interface UserRepository extends JpaRepository<User,Long> {}

package com.zkb.service; import com.zkb.entity.User; import java.util.List; public interface UserService { public void deleteUser(Long id); List<User> getList();}

package com.zkb.service.impl; import com.zkb.dao.UserRepository;import com.zkb.entity.User;import com.zkb.service.UserService;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Service; import java.util.List; @Servicepublic class UserServiceImpl implements UserService { @Autowired private UserRepository userRepository; @Override public void deleteUser(Long id) { System.out.println(userRepository); userRepository.deleteById(id); } @Override public List<User> getList() { return userRepository.findAll(); }}

package com.zkb.controller; import com.zkb.entity.User;import com.zkb.service.UserService;import io.swagger.annotations.Api;import io.swagger.annotations.ApiOperation;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.web.bind.annotation.PostMapping;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RequestParam;import org.springframework.web.bind.annotation.RestController; import java.util.List; @RestController@RequestMapping('/user')@Api(value = 'user',tags = 'user')public class UserController { @Autowired private UserService userService; @PostMapping('/del') @ApiOperation(value='删除',notes = '删除') public String delete(@RequestParam('id') Long id){ userService.deleteUser(id); return 'true'; } @PostMapping('/getList') @ApiOperation(value='查询所有',notes = '查询所有') public List<User> getList(){ return userService.getList(); }}

package com.zkb.conf; import io.swagger.annotations.ApiOperation;import io.swagger.models.auth.In;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;import springfox.documentation.builders.ApiInfoBuilder;import springfox.documentation.builders.PathSelectors;import springfox.documentation.builders.RequestHandlerSelectors;import springfox.documentation.service.ApiInfo;import springfox.documentation.service.ApiKey;import springfox.documentation.service.Contact;import springfox.documentation.spi.DocumentationType;import springfox.documentation.spring.web.plugins.Docket;import springfox.documentation.swagger2.annotations.EnableSwagger2; import java.util.Arrays;import java.util.List; @Configuration@EnableSwagger2public class SwaggerApp { @Bean public Docket createRestApi1() { return new Docket(DocumentationType.SWAGGER_2).enable(true).apiInfo(apiInfo()).select().apis(RequestHandlerSelectors.withMethodAnnotation(ApiOperation.class)).apis(RequestHandlerSelectors.basePackage('com.zkb.controller')).paths(PathSelectors.any()).build().securitySchemes(apiKeyList()).groupName('接口中心'); } private ApiInfo apiInfo() { return new ApiInfoBuilder().title('API').contact(new Contact('XXXXX', 'http://XXXXXX.XXXX/', '')).version('1.0').description('API 描述').build(); } private List<ApiKey> apiKeyList() { return Arrays.asList(new ApiKey('登录token', 'token', In.HEADER.name()),new ApiKey('设备类型(android,ios,pc)---必填', 'deviceType', In.HEADER.name())); }}

package com.zkb;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;import springfox.documentation.swagger2.annotations.EnableSwagger2;@SpringBootApplication@EnableSwagger2public class App { public static void main(String[] args) { SpringApplication.run(App.class,args); }}

CREATE TABLE `t_user` ( `id` bigint NOT NULL AUTO_INCREMENT, `username` varchar(50) COLLATE utf8mb4_general_ci DEFAULT NULL, `password` varchar(50) COLLATE utf8mb4_general_ci DEFAULT NULL, PRIMARY KEY (`id`) USING BTREE) ENGINE=InnoDB AUTO_INCREMENT=1214893367637352451 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_general_ci;

非常简单的一张表，注意数据库名称

到这里就已经实现了一个非常简单的jpa demo了

当然我这里只是指路，让知怎么用

补充：SpringBoot使用JPA实现增删查改

SpringBoot2.3.0

JDK1.8

IDEA2020.1.2

MySQL5.7

<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-jpa</artifactId></dependency><dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-thymeleaf</artifactId></dependency><dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-validation</artifactId></dependency><dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId></dependency><dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <scope>runtime</scope></dependency><dependency> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId> <optional>true</optional></dependency><dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> <exclusions> <exclusion> <groupId>org.junit.vintage</groupId> <artifactId>junit-vintage-engine</artifactId> </exclusion> </exclusions></dependency>

1、升级到SpringBoot2.2，spring-boot-starter-test默认使用JUnit 5作为单元测试框架 ，写单元测试时注解@RunWith(Spring.class)升级为@ExtendWith(SpringExtension.class)

2、升级到SpringBoot2.3，hibernate-validator从spring-boot-starter-web移除，需要单独引入

3、升级到SpringBoot2.3，MySQL驱动由com.mysql.jdbc.Driver变更为com.mysql.cj.jdbc.Driver;同时，数据源url需要添加serverTimezone=UTC&useSSL=false参数

3、升级到SpringBoot2.x，默认不自动注入HiddenHttpMethodFilter，需要设置spring.mvc.hiddenmethod.filter.enabled=true开启PUT、DELETE方法支持

应用程序配置如下：

spring.application.name=springbootjpamanagement.endpoints.jmx.exposure.include=*management.endpoints.web.exposure.include=*management.endpoint.health.show-details=always# 应用服务 WEB 访问端口server.port=8080# Actuator Web 访问端口management.server.port=8081# mysql settingspring.datasource.driver-class-name=com.mysql.cj.jdbc.Driverspring.datasource.url=jdbc:mysql://localhost:3306/springbootjpa?serverTimezone=UTC&useSSL=falsespring.datasource.username=usernamespring.datasource.password=password# JPA settingspring.jpa.properties.hibernate.hbm2ddl.auto=updatespring.jpa.properties.hibernate.dialect=org.hibernate.dialect.MySQL5InnoDBDialectspring.jpa.show-sql=true# thymeleaf settingspring.thymeleaf.cache=false# delete、put方法支持spring.mvc.hiddenmethod.filter.enabled=true三、定义实体

使用@Entity标记实体类

import lombok.Data;import javax.persistence.*;import javax.validation.constraints.NotEmpty;import java.io.Serializable;@Entity@Datapublic class Article extends BaseEntity implements Serializable { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id; @Column(nullable = false, unique = true) @NotEmpty(message = '标题不能为空') private String title; @Column(nullable = false) private String body;}

为了自动添加创建日期、修改日期、创建人及修改人，我们把创建、修改信息放到父类中由实体类继承，并开启SpringBoot的自动审计功能，将创建/修改信息自动注入

1、定义实体类的父类,@CreatedDate、@LastModifiedDate、@CreatedBy、@LastModifiedBy标注相应字段

import org.hibernate.annotations.Columns;import org.springframework.data.annotation.CreatedBy;import org.springframework.data.annotation.CreatedDate;import org.springframework.data.annotation.LastModifiedBy;import org.springframework.data.annotation.LastModifiedDate;import org.springframework.data.jpa.domain.support.AuditingEntityListener;import javax.persistence.Column;import javax.persistence.EntityListeners;import javax.persistence.MappedSuperclass;@MappedSuperclass@EntityListeners(AuditingEntityListener.class)public class BaseEntity { @CreatedDate private Long createTime; @LastModifiedDate private Long updateTime; @Column(name = 'create_by') @CreatedBy private String createBy; @Column(name = 'lastmodified_by') @LastModifiedBy private String lastmodifiedBy; public Long getCreateTime() { return createTime; } public void setCreateTime(Long createTime) { this.createTime = createTime; } public Long getUpdateTime() { return updateTime; } public void setUpdateTime(Long updateTime) { this.updateTime = updateTime; } public String getCreateBy() { return createBy; } public void setCreateBy(String createBy) { this.createBy = createBy; } public String getLastmodifiedBy() { return lastmodifiedBy; } public void setLastmodifiedBy(String lastmodifiedBy) { this.lastmodifiedBy = lastmodifiedBy; }}@MappedSuperclass注解：

作用于实体类的父类上，父类不生成对应的数据库表

标注@MappedSuperclass的类不能再标注@Entity或@Table注解，也无需实现序列化接口

每个子类（实体类）对应一张数据库表，数据库表包含子类属性和父类属性

标注@MappedSuperclass的类可以直接标注@EntityListeners实体监听器

作用范围仅在标注@MappedSuperclass类的所有继承类中，并且实体监听器可以被其子类继承或重载

开启JPA的审计功能，需要在SpringBoot的入口类标注@EnableJpaAuditing

创建日期、修改日期有默认方法注入值，但创建人和修改人注入则需要手动实现AuditorAware接口:

@Configurationpublic class BaseEntityAuditor implements AuditorAware<String> { @Override public Optional<String> getCurrentAuditor() { return ''; }}四、DAO层实现

JPA支持通过约定方法名进行数据库查询、修改：

import org.springframework.data.jpa.repository.JpaRepository;import springbootjpa.entity.Article;public interface ArticleRepository extends JpaRepository<Article, Long> { Article findById(long id);}

通过约定方法名查询，只需实现JpaRepository接口声明查询方法而不需要具体实现

此外，可以在方法上标注@Query实现JPQL或原生SQL查询

JpaRepository<T, ID>,T表示要操作的实体对象，ID表示主键。该接口继承了分页排序接口PadingAndSortRepository,通过构建Pageable实现分页查询：

@Autowiredprivate ArticleRepository articleRepository;@RequestMapping('')public ModelAndView articlelist(@RequestParam(value = 'start', defaultValue = '0') Integer start, @RequestParam(value = 'limit', defaultValue = '5') Integer limit) { start = start < 0 ? 0 : start; Sort sort = Sort.by(Sort.Direction.DESC, 'id'); Pageable pageable = PageRequest.of(start, limit, sort); Page<Article> page = articleRepository.findAll(pageable); ModelAndView modelAndView = new ModelAndView('article/list'); modelAndView.addObject('page', page); return modelAndView;}

如果根据某一字段排序，可以用Sort.by方法构建Sort对象；如果根据多个字段排序，首先构建Sort.Order数组List<Sort.Order>,然后再传入Sort.by方法构建Sort对象。

PageRequest.of方法生成Pageable对象

import org.springframework.beans.factory.annotation.Autowired;import org.springframework.data.domain.Page;import org.springframework.data.domain.PageRequest;import org.springframework.data.domain.Pageable;import org.springframework.data.domain.Sort;import org.springframework.stereotype.Controller;import org.springframework.web.bind.annotation.*;import org.springframework.web.servlet.ModelAndView;import springbootjpa.entity.Article;import springbootjpa.repository.ArticleRepository;@Controller@RequestMapping('/article')public class ArticleController { @Autowired private ArticleRepository articleRepository; @RequestMapping('') public ModelAndView articlelist(@RequestParam(value = 'start', defaultValue = '0') Integer start, @RequestParam(value = 'limit', defaultValue = '5') Integer limit) { start = start < 0 ? 0 : start; Sort sort = Sort.by(Sort.Direction.DESC, 'id'); Pageable pageable = PageRequest.of(start, limit, sort); Page<Article> page = articleRepository.findAll(pageable); ModelAndView modelAndView = new ModelAndView('article/list'); modelAndView.addObject('page', page); return modelAndView; } @RequestMapping('/add') public String addArticle() { return 'article/add'; } @PostMapping('') public String saveArticle(Article article) { articleRepository.save(article); return 'redirect:/article'; } @GetMapping('/{id}') public ModelAndView getArticle(@PathVariable('id') Integer id) { Article article = articleRepository.findById(id); ModelAndView modelAndView = new ModelAndView('article/show'); modelAndView.addObject('article', article); return modelAndView; } @DeleteMapping('/{id}') public String deleteArticle(@PathVariable('id') long id) { System.out.println('put 方法'); articleRepository.deleteById(id); return 'redirect:/article'; } @GetMapping('edit/{id}') public ModelAndView editArticle(@PathVariable('id') Integer id) { Article article = articleRepository.findById(id); ModelAndView modelAndView = new ModelAndView('article/edit'); modelAndView.addObject('article', article); return modelAndView; } @PutMapping('/{id}') public String editArticleSave(Article article, long id) { System.out.println('put 方法'); article.setId(id); articleRepository.save(article); return 'redirect:/article'; }}

因为<form>表单只能发送GET或POST请求，spring3引入一个监听器HiddenHttpMethodFilter来将POST请求转换为PUT或POST请求。

SpringBoot2.x开始默认不自动注入HiddenHttpMethodFilter，需要设置spring.mvc.hiddenmethod.filter.enabled=true开启PUT、DELETE方法支持

配置完后，前端页面需要在表单中加入隐藏域，表明实际请求方法：

<!-- DELETE 请求 --><form method='POST' action=''><input type='hidden' name='_method' value='delete'></form><!-- PUT 请求 --><form method='POST' action=''><input type='hidden' name='_method' value='put'></form>六、其他th:value和th:field区别：

th:value解析成html，表现为：value='${th:value}'

th:field解析成html，表现为：name='${th:name}' value='${th:value}'

以上为个人经验，希望能给大家一个参考，也希望大家多多支持好吧啦网。如有错误或未考虑完全的地方，望不吝赐教。